Building block



FIG. 1 is a right side perspective of the building block of the design of the present invention;

FIG. 2 is a left side perspective view thereof;

FIG. 3 is a front elevational view thereof;

FIG. 4 is a rear elevational view thereof;

FIG. 5 is a right side elevational view thereof;

FIG. 6 is a left side elevational view thereof;

FIG. 7 is a top plan view thereof;

FIG. 8 is a bottom view thereof;

FIG. 9 is a right side perspective of a modified embodiment of the building block of the design of the present invention;

FIG. 10 is a left side perspective view thereof;

FIG. 11 is a front elevational view thereof;

FIG. 12 is a rear elevational view thereof;

FIG. 13 is a right side elevational view thereof;

FIG. 14 is a left side elevational view thereof;

FIG. 15 is a top plan view thereof; and,

FIG. 16 is a bottom view thereof. 

The ornamental design for a building block, as shown and described. 